AP® Physics 1 & 2

Point-Mass Experiment

APPH12-KNCEVX

Created for Albert.io. Copyright 2016. All rights reserved.

A "point-mass" is assembled for a certain experiment by connecting a small, heavy rock to the end of a long, lightweight rod. The assembly is held horizontally, in the position shown in the side-view diagram above, and released to pivot about an axis fixed through its left end.

At the moment it is released to swing downward, the instantaneous angular acceleration of the assembly is measured to be $4 { rad }/{ { s }^{ 2 } }$.

In a second trial of the experiment, the rod is replaced by a new rod with twice the length of the original rod, but everything else about the second trial is identical to the first trial. The diagram below shows the second trial assembly when it is held horizontally.

In the second trial, what is the assembly's instantaneous angular acceleration at the moment it is released from rest?